It can be further understood by the cut of the working drawing, which shows most of the improvements, except the present form of the ore spreader, which is as per cut below, and was devised, so that for gold ores, a silverplated copper plate could be placed over the entire surface of the spreader, the top board B, with blocks attached being put on the plate; also the copper well C, in which is caught quicksilver which may escape from the main plate above; when the plate is to be cleaned, the top board and blocks are removed; this is only done occasionally.

The ore with water is delivered on the belt by means of the spreader No. 1, in working drawing, which shakes with the table, and distributes the pulp uniformly across the belt. A small amount of clean water is distributed by No. 2, which is a wooden trough in which is a perforated pipe. A depth of three-eighths to one-half inch of sand and water is constantly kept on the table. The main shaft, H, should be given the proper speed for each kind of ore, and once established, it should be kept uniform; this speed will be between 180 and 200 revolutions of the crank shaft per minute, with one inch throw.

The up-hill travel or progressive motion varies from 3 feet to 12 feet a minute, according to the ore, and the grade or inclination of the table is from 3 inches to 6 inches in 12 feet, varying with the ore. The inclination can be changed at will, by wedges at the foot of the machine. The motion, the water used, the grade, and the up-hill travel should be regulated for every ore individually, but once established no further trouble will be experienced in the manipulation.

The main body of the belt suffers hardly any wear, as it merely moves its own weight slowly around the freely revolving rollers.

For one machine, inch of water (miner's measure), or 6 gallons a minute, including the water used in crushing, is as large an amount as is ever needed on any material, while on some ores 3 gallons will answer; and by returning the water from the settled tailingsgallon will keep up

the loss.

The boiler for a 5-stamp mill with 2 concentrators consumes 1 gallon a minute, hence where water is very scarce 2 gallons a minute can supply 5 stamps, 2 Frue vanners, and the boiler.

As regards the capacity of the Frue vanner, about 6 tons per 24 hours passing a 40-mesh screen is as much as it is advisable to treat. If the battery of 5 stamps does its duty, the quantity crushed is largely in excess of 6 tons. For this reason, the best practice is to put 2 Frue vanners to 5

stamps, if the stamps are heavy and the sulphurets high grade and difficult to save; and in such event the pulp is divided, one half passing on each. The machines are generally placed in a double row, on the same level, head to head, as per cut of mill.

In many cases 3 vanners to 10 stamps will yield entirely satisfactory work, and where the gangue is light, or the stamps not heavy, one vanner treats all the ore crushed with 5 stamps, and does perfect work; e. g., in the Empire mill of 80 stamps, at Plymouth, in Amador County, 16 Frues are concentrating all the ore crushed by the 80 stamps, and the tailings assay merely a trace. No sizing of the ore is needed; the pulp passes directly from the stamps on the copper plates (if used), and thence on the

vanners.

In running the machine the point of greatest importance is regularity; regularity in speed; regularity in the delivery of pulp on the belt, and regularity in the supply of clear water. The necessity of this is obvious to any one who thinks of the work to be done by an automatic machine.

With hand labor the judgment of man regulates the means employed in conformity with varying conditions; but in a machine, the object of which is to supersede hand labor, it becomes obvious that having once adjusted the movements to effect a certain object under certain conditions, the desired result can only be attained by the maintenance of the necessary conditions.

In this concentrator, supposing the inclination of the belt to be fixed for a certain class of material, the regulation of the work to be accomplished is effected by three things, viz.: the speed with which the belt revolves, the